The Section runs the Laboratory of Muscle Enzyme Histochemistry that processes up to 300 muscle and nerve biopsies per year for diagnostic studies. Examined muscle specimens are from patients with neuromuscular manifestations related to systemic autoimmune, viral, metabolic, endocrine or infectious diseases, and from patients with primary neuromuscular disorders, such as polymyositis, dermatomyositis, neurogenic muscular atrophies, muscular dystrophies, post-polio syndrome, mitochondrial encephalomyopathies and biochemical or genetic muscle diseases such as central core disease or hypertrophic cardiomyopathy. The laboratory is also involved in the following immunologic, biochemic and virologic studies that examine the susceptibility of the muscle and nerve to immune or viral mediated injuries: (a) Study the regeneration of human muscle in health and disease and the maturation of satellite cells by examining the expression of neural cell adhesion molecules and laminins; (b) study the susceptibility of muscle and nerve to infection with retroviruses and the ability of HIV or HIV-infected lymphoid cells to infect human myotubes in culture and induce expression of MHC-antigens; (c) study the expression of the poliovirus receptor in human muscle and the ability of the poliovirus to infect and replicate in human myotubes; (d) study the effects of cytokines and lymphokines on human muscle myotubes and examine the role of LCAM-L in enhancing myocytotoxicity by promoting the adhesion of cytotoxic T cells to myotubes; (e) study the toxicity of AZT to muscle mitochondria by applying AZT to human muscle in culture; (f) study the effect of L- carnitine in reversing the mitochondrial abnormalities induced by AZT on myotubes and (g) use animal models to study: i) the pathogenesis of retrovirus-induced inflammatory myopathy by examining muscles from monkeys infected with the simian immunodeficiency virus; ii) the mechanism of AZT- induced mitochondrial myopathy by examining the structural, metabolic and functional alterations in the muscle mitochondria of healthy rats injected with AZT; and iii) the effect of L-carnitine in reversing or improving the AZT-induced myopathy in the rats.